The Targeting-Tracking System (T&T), also known as Advanced Fire Control System, is the system that provides sensory and targeting information for a combat unit. Introduced circa 2439[1], all modern combat units (BattleMechs, Combat Vehicles, Aerospace Fighters, Battle Armor, etc.) include some form of T&T as part of their basic sensor suite.

On BattleMechs, the T&T incorporates a variety of sophisticated sensors with dedicated computers to process their data. Primary amongst these are thermal imaging, light amplification, radar and magnetic anomaly sensors. These are supplemented by secondary sensors, including motion detectors, chemical sniffers and others, all of which is interpreted and presented to the MechWarrior in an easy-to-understand format, whether on their cockpit displays or Neurohelmet's heads-up display. The T&T is capable of telling friend from foe and classifying other units, even speculating on the exact variant. The intuitiveness of the system is responsible for the Mad Cat moniker given to the Timber Wolf during the Clan Invasion, since it appeared to combine aspects of both the Marauder and Catapult. The T&T is also capable of sharing basic sensory data with another unit, though not to the same degree as available with Command, Control and Communications (C3) systems, and the sensory information can be saved via battleROM for later viewing.[2]

During the destruction of the Succession Wars, some of the advanced fire control technology common during the Star League became lostech, greatly affecting the way battles were fought. Many systems capable of great precision over long distances could no longer be built or maintained, and often had to be replaced with more primitive examples. Towards the end of the era, many 'Mechs had T&T systems which themselves were centuries old, often cobbled together with parts from different machines just so they could work. Even with weapons whose theoretical maximum range was the horizon, their effective range might be greatly reduced depending on the type of target at which the 'Mech was shooting.[3] For example, at a distance of over 800m, a Shadow Hawk might have trouble landing accurate hits on another 'Mech with its autocannon, but would have no issue with a stationary tower.[4] This technological decline also affected aerospace combat, though it be fought on a much grander scale: enemy craft might engage each other at distances of up to tens of thousands of kilometers, but the accuracy of their shots would be based on their computers' ability to predict where the enemy would be and have their fire intersect that point, and so the more evasive an opponent was the harder they were to destroy.[5] Ground-bound aerospace units found their fire control systems impacted by the same factors which limited 'Mech systems, greatly reducing their weapons' range.[6]

As IndustrialMechs and Support Vehicles are designed primarily for non-combat use, they usually do not include an Advanced Fire Control System, although they can be modified. Industrial 'Mechs come standard with what is known as a Basic Fire Control System, which dates back to before the introduction of T&T. While sophisticated systems for their day and still sufficient for combat, they are greatly affected by the intrinsic electronic warfare capabilities of 31st century combat units and are incompatible with peripheral targeting systems. Changing out a Basic Fire Control System for an Advanced Fire Control System amounts to a simple swap and is easily accomplished, although only done so in the rare cases where an Industrial 'Mech is actually armed.
Support vehicles do not come standard with with any FCS, and while they can be modified or built with either the basic or advanced system they do so less efficiently.[1]

In Classic BattleTech play a Targeting-Tracking or Advanced Fire Control System is known simply as Sensors and assumes the presence and functionality of this piece of equipment in all combat units, granting no bonus. In the event of a critical hit a +2 Gunnery skill penalty takes effect; after a second critical hit the unit can no longer fire. An Industrial 'Mech or Support Vehicle equipped with a Basic Fire Control System receives a +1 penalty, while a Support Vehicle without any fire control system receives a +2 to-hit penalty.[7] Units without an Advanced Fire Control System may not use Artemis IV FCS, Artemis V FCS, Targeting Computers, Command, Control and Communications (C3) systems, or Active Probes.[1]

In construction rules all combat units automatically come with an Advanced Fire Control System which takes up no weight. Industrial 'Mechs automatically come with a Basic Fire Control System, which weighs equivalent to five percent of all carried Medium and Heavy weapons and reduces by one the crew needed for Medium weapons to a minimum of one. Installing an Advanced Fire Control System weighs the same but doubles the cost of the cockpit. Support Vehicles do not come automatically with any fire control systems. They may install a Basic Fire Control System, weighing equivalent to five percent of all carried Medium and Heavy weapons, or an Advanced Fire Control System, weighing equivalent to ten percent of all carried Medium and Heavy weapons.[1] (An Advanced Fire Control system for a Support Vehicle mounting only a Gauss Rifle would thus weigh 1.5 tons.)